A call for a reported cardiac arrest came in at 6:38am, Fire Department sources said.

Two weeks ago, Epstein, 66, was placed on suicide watch after he was found nearly unconscious in his cell with injuries to his neck.

There was some question about whether the incident was a suicide attempt or an assault, and investigators noted that the marks on his neck were "more consistent with being choked than hanging yourself," a source told the New York Post.

Department of Justice spokesman Lee Plourde refused to say whether that incident was ruled a suicide attempt or an assault.

He said Epstein was never treated outside MCC after that incident, disputing reports.

Mr Plourde confirmed that Epstein was not "currently" on suicide watch in his cell.

The billionaire financier was being held without bail pending his trial on child sex-trafficking charges.

Jeffrey Epstein, centre, appears in court. Picture: AP

Some reports suggest cameras inside the Manhattan Correctional Centre malfunctioned around the time of his suicide.

The MCC has some of the tightest security in the US and has housed notorious criminals including Joaquin "El Chapo" Guzman, mob boss John Gotti, the World Trade Center bombers and Ponzi scheme mastermind Bernie Madoff.

Disgraced financier Bernie Madoff. Picture: Supplied

Attorney General Bill Barr said he was "appalled" to learn Epstein was able to commit suicide in his federal jail cell.

"Mr Epstein's death raises serious questions that must be answered. In addition to the FBI's investigation, I have consulted with the Inspector General who is opening an investigation into the circumstances of Mr Epstein's death," Mr Barr said.

Epstein was busted on July 6 over the alleged sexual abuse of dozens of young girls in his Upper East Side townhouse and his waterfront mansion in Palm, Beach, Florida, between 2002 and 2005.

He pleaded not guilty and faced up to 45 years in prison.

Many people on social media started to question how he was able to kill himself.

Predator Jeffrey Epstein killed himself. On behalf of the victims I represent, we would have preferred he lived to face justice.Our civil cases can still proceed against his estate. Victims deserve to be made whole for the lifelong damage he caused. We’re just getting started.

I am calling today for the administrators of Jeffrey Epstein’s estate to freeze all his assets and hold them for his victims who are filing civil cases. Their lives have been shattered by his sexual assaults, their careers derailed. They deserve full and fair compensation NOW.

I guess they think a country dumb enough to elect Trump is stupid enough to believe Jeffrey Epstein committed suicide. Or not. Love that they did it on the traditional Friday night/early Saturday morning “document dump” time when they know the fewest people will follow it. pic.twitter.com/GRpCOlh5B1

William Barr’s DOJ runs the jail where #JeffreyEpstein was able to commit “suicide”. We know that Barr’s good buddy, Tang is on the list of high profile men who “knew” Epstein AND the underage girls he trafficked for sex. We all know how Barr protects his president. #SITMAC

Epstein victim Jennifer Araoz responds: “I am angry Jeffrey Epstein won’t have to face his survivors of his abuse in court. We have to live with the scars of his actions for the rest of our lives, while he will never face the consequences of the crimes he committed...”

I never subscribe to conspiracy theories but this is just ridiculous. Jeffrey Epstein was on suicide watch but somehow manages to still kill himself? He was probably murdered or somebody encouraged him to do it to protect a bunch of rich and powerful pedophiles. #EpsteinSuicide

Remember the scene in the Godfather? Tom Hagen who talks of Roman traitors to Frankie Pentangeli who then kills himself... life imitating art? Powerful people didn’t want Epstein to talk. I want to find out who.

Epstein's arrest last month launched separate investigations into how authorities handled his case initially when similar charges were first brought against him in Florida more than a decade ago.

US Labor Secretary Alexander Acosta resigned last month after coming under fire for overseeing that deal when he was US attorney in Miami.

The 66-year-old had pleaded not guilty.

His death came as thousands of documents were unsealed on Friday in connection with a defamation case against his alleged recruiter revealed dozens of high-profile names that a self-identified victim, Virginia Giuffre, said she was forced to perform sex acts with, from former Maine Senator George Mitchell and ex-New Mexico Governor Bill Richardson, money manager Glenn Dubin and MIT professor Marvin Minksy.

The financier once boasted about having high profile friends, including US President Donald Trump, former US president Bill Clinton and Prince Andrew.

In 1992, Mr Trump directed Florida businessman George Houraney to organise a "calendar girl" competition at Mar-a-Lago. After 28 female contestants were procured, he revealed that the other guests were just "him and Epstein", The New York Times reported.

Donald Trump and his then girlfriend Melania Knauss, financier Jeffrey Epstein, and British socialite Ghislaine Maxwell pose together at the Mar-a-Lago club, Palm Beach, Florida, February 12, 2000. Picture: Getty

Then, in a much-quoted 2002 New York Magazine interview, Mr Trump described Epstein as a "terrific guy" and even acknowledged that he liked women "on the younger side".

"I've known Jeff for 15 years. Terrific guy. He's a lot of fun to be with. It is even said that he likes beautiful women as much as I do, and many of them are on the younger side," he told the magazine.

Last month, Mr Trump said he had not spoken to Mr Epstein for 15 years.

"I knew him like everybody in Palm Beach knew him," Mr Trump said. "I was not a fan."

The high security Manhattan Correctional Centre in New York City. Picture: Supplied

WHO WAS JEFFREY EPSTEIN

Epstein lived on a 100-acre private island in the Caribbean and one of the biggest mansions in New York valued at $US56 million.

A college dropout, he started as a physics and mathematics teacher at the pristigious Dalton School in the Upper East Side of Manhattan.

While teaching at the school, Epstein became acquainted with Alan Greenberg, the chief executive officer of investment bank Bear Stearns, whose son and daughter were going to the school, and who offered him a job as a low-level junior assistant to a floor trader in 1976.

He was reportedly asked to leave Bear Sterns for unknown reasons in 1981 but remained close with Mr Greenberg and his sucessor Jimmy Cayne.

He founded his own consulting firm, Intercontinental Assets Group, that same year and in 1988 founded his own financial management firm, J. Epstein & Company. The company was formed to manage the assets of clients with more than $US1 billion in net worth.

One of those clients was Leslie Wexner, chairman and CEO of L Brands and Victoria's Secret.

Wexner trusted Epstein so much he gave him power of attorney to run his finances.

He is said to have dated publishing heir Ghislaine Maxwell, whom he had met by 1991. Maxwell was implicated by several of Epstein's accusers as procuring or recruiting underage girls in addition to being his girlfriend.

Ghislaine Maxwell. Picture: Getty

If you are experiencing mental health issues or suicidal feelings contact Lifeline on 13 11 14 or BeyondBlue 1300 224 636. If it is an emergency please call 000.

This article originally appeared in the New York Post and is republished here with permission